Malignant tumors are often treated by surgical resection of the tumor to remove as much of the tumor as possible. Infiltration of the tumor cells into normal tissue surrounding the tumor, however, can limit the therapeutic value of surgical resection because the infiltration can be difficult or impossible to treat surgically. Radiation therapy can be used to supplement surgical resection by targeting the residual tumor margin after resection, with the goal of reducing its size or stabilizing it.
Radiation therapy can be administered through one of several methods, or a combination of methods, including external-beam radiation, stereotactic radiosurgery, and permanent or temporary brachytherapy. The term “brachytherapy,” as used herein, refers to radiation therapy delivered by a source of therapeutic rays inserted into the body at or near a tumor or other proliferative tissue disease site.
One interstitial brachytherapy therapy system is the Mammosite® system, provided by Hologic, Inc. of Bedford, Mass. The MammoSite system includes a catheter shaft with an inflatable balloon mounted on its distal end. A lumen extends within the catheter shaft, into the balloon. The catheter shaft is inserted into a body so that the balloon is positioned within a resected cavity. The balloon is subsequently inflated and radioactive material, for example in the form of one or more radioactive seeds, is loaded into the lumen for radiation delivery.
A typical breast brachytherapy radiation treatment plan involves insertion of the balloon by a doctor during a lumpectomy. During a series of follow up visits, a radiologists delivers radiation dosing to the patient by loading radioactive material into the balloon catheter for a determined period of time to achieve a desired dosage. The brachytherapy catheter system is removed upon completion of treatment. Although the catheter must have sufficient rigidity for insertion into the resected cavity, because the brachytherapy catheter system is left in place between treatments it is desirable that the catheter be flexible; rigid catheter designs not only cause patient discomfort but may result in undesirable torque of the balloon which results in a shift of balloon location between treatments.
In single lumen brachytherapy catheters, the lumen is generally centered within the balloon such that the balloon generates isodose profiles in the target tissue that are substantially symmetrical, similar in shape to the inflated balloon. However, symmetric dosing may not always be desirable, as the resection cavity may not be uniform or regular in shape and size. Asymmetric dosing methods, such as those described in U.S. Pat. No. 6,749,555 include catheters with multiple lumens, where radioactive seeds may be placed within the different lumens to achieve different dosing profiles. Methods and systems for using multiple lumens for interstitial breast brachytherapy are also described by Lubock in U.S. Patent application publication number 20070167667, and by Cutrer in U.S. Patent application publication number 20070142694.
One problem with existing multi-lumen designs is that they increase the rigidity of the catheter, concomitantly increasing patient discomfort and the occurrence of balloon movement subsequent to initial placement. It would be desirable to identify a design for multi-lumen brachytherapy device which overcomes the problems of the prior art.